2003 GMC Envoy FRONT OF ENGINE CLICKING NOISE

LOAD CLICKING NOISE - APPROX 1 SEC INTERVIALS - FRONT OF ENGINE - IDLE OR VERY LOW RPM - DEVELOLPS AFTER SHORT WARM UP - CAN CONTINUE CONSTANTLY OR SHORT REPS OF 20 TO 30 WITH A SHORT BREAK IN BETWEEN.
STARTED @ 50 K.
REMOVED BELT, NO CHANGE
SOUNDS LIKE INSIDE TIMING COVER (POSSIBLY A CHAIN TENSIONER?)

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Tuesday, February 3rd, 2009 AT 9:04 AM

1 Reply

BRIAN 1

EXPERT

1,070 POSTS

Try this first sounds like your problem, Some customers may comment on an underhood tick noise heard while the vehicle is idling. Technicians may find that the noise does not increase or decrease with changes in the engine idle RPM. The tick noise occurs at approximately one second intervals.

Cause
This condition may be caused by the electro-viscous fan clutch control function of the Powertrain Control Module (PCM) attempting to keep the fan speed between 300-600 revolutions per minute (RPM). At idle, the cooling fan speed will drag to approximately 500 RPM then oscillate between 300 and 600 RPM. When the fan speed drops below 500 RPM, the PCM will pulse the fan control solenoid. The pulsing of the solenoid is the cause of the ticking noise.

Reprogram the PCM.
DON'T Replace the engine cooling fan clutch.

Command the cooling fan off. If the ticking noise goes away, the pulsing of the cooling fan clutch is the source of the noise.

" The cooling fan clutch electrical connector, located on the cooling fan shroud, may be disconnected with the engine off. If the ticking noise goes away, the pulsing of the cooling fan clutch is the source of the noise. Be sure to clear any Diagnostic Trouble Codes (DTCs) that may have set while the cooling fan clutch is disconnected. Reprogram the PCM with an updated software calibration. Post back with any other questions.